The present invention pertains to vertical cavity surface emitting lasers (VCSELs) and particularly to tunnel junction VCSELs having long wavelengths, namely, 1200 to 1800 nanometer wavelengths.
A long wavelength VCSEL having a tunnel junction and a thick mirror layer is difficult to isolate because of the high doping used in the tunnel junction. Island isolation or trenches can provide direct current (D.C.) isolation for such VCSELs. To reduce capacitance of the VCSEL an implant needs to be used; however, it will not adequately compensate the tunnel junction. Because the implant can go deeper than the tunnel junction into the p region and down to the active region it can form an insulating region under the tunnel junction which reduces the capacitance. Some VCSEL isolation is shown in U.S. Pat. No. 5,903,588. U.S. Pat. No. 5,903,588 issued May 11, 1999, and entitled xe2x80x9cLaser with a Selectively Changed Current Confining Layer,xe2x80x9d is expressly incorporated herein by reference into this description.
An isolation implant used for isolation of a VCSEL should go through and past the tunnel junction of the VCSEL into and optimally through the p layer. This implant results in a semi-insulating region that reduces capacitance under the tunnel junction. Internal trenches about the VCSEL aperture can be utilized to reduce a required oxidation distance and thus reduce variability of the aperture diameter.